The rule against an expert giving an opinion on a matter that is for the jury or the judge to determine is becoming very strained

It had long been a rule of evidence at common
law that a witness – and that included expert witnesses – should not give
evidence in relation to what is termed the ‘ultimate issue’ (i.e. any fact
in issue) in a case. The rule applied in both the civil and criminal courts,
and was based upon the principle that a matter that is for the jury (or the
judge) to decide should not be usurped by a witness.

So, for example, a fingerprint expert witness
could state, with varying degrees of certainty, whether fingerprints found on a
murder weapon were a match for those of the accused. He was not, however,
permitted to go beyond this and say that, in his opinion, the accused was the
murderer. Guilt or innocence was a matter for the jury to decide, and the
prohibition on expert witnesses addressing the ultimate issue was designed to
prevent trial by jury being supplanted by trial by expert.

In DPP -v- A and BC Chewing Gum1,
Lord Parker CJ said that, while an expert in child psychiatry was competent to
give an opinion on the effect of battle scenes on children, it would be wrong
for the expert witness to give his opinion on whether any of the defendant
company’s products containing such images actually tended to corrupt or deprave
‘... because that final stage was a matter which was entirely for the
justices’.

This basic premise of the ultimate issue rule was also
outlined by Cresswell J in the Ikarian Reefer2 in 1993. The
expert should only give evidence in relation to matters within his expertise
and on issues not within the ordinary experience of the jury. If the jury is
capable of forming an opinion without the assistance of an expert because the
matter is within their own experience or knowledge, then expert opinion is not
necessary.

Weakening
of the rule

For some time there has been an ongoing and
steady weakening of the rule against expert opinion on the ultimate issue. The
1972 Civil Evidence Act made expert opinion on the ultimate issue admissible in
civil cases, giving effect to the 1970 Report of the Law Reform Committee on
Evidence of Opinion and Expert Evidence. This report recommended that ‘... a
statement by an expert witness... shall not be inadmissible upon the ground
only that it expressed his opinion on the issue in the proceedings...’. In
criminal cases, the abolition of the rule was recommended by the Criminal Law
Revision Committee in its Eleventh Report (Cmnd 4991 (1972) p. 155), but
this recommendation was never put into effect.

However, even in civil cases, there remained
definite limits on the extent to which opinion on the ultimate issue would be
admissible, and the common law rule continued to exert pressure in determining
the line between what was acceptable and what was not.

In Pride Valley Foods Ltd -v- Hall and
Partners3, an expert witness in a construction law case gave an
opinion on what he would have done if he had been in a similar position to the
defendant. In doing so, he was directly addressing questions relating to the
ultimate issue. Toumlin J said that these were not questions for expert witnesses
but were matters for the court to decide. The expert, he said, purported to
make findings of fact on matters that are for the judge, and that his report
offended against the established basis on which experts should give their
evidence.

Complexity
rules

However, with increasingly complex areas of evidence, and
particularly those involving medical malpractice, fraud or forensic science,
the boundaries between acceptable expert opinion and opinion that addresses the
ultimate issue have become blurred. In fraud cases, for example, expert
accountants have given opinions which effectively state that there can be no
rational, honest explanation for the transactions under consideration, thus
inferring that the only remaining explanation is one of fraud.

In the same year as the Ikarian Reefer
case, Lord Taylor stated, as an aside, that:

‘... the
rationale behind the supposed prohibition is that the expert should not usurp
the functions of the jury. But since counsel can bring the witness so close to
opining on the ultimate issue that the inference as to his view is obvious, the
rule can only be a matter of form rather than substance’.

For example, in a medical malpractice case an
expert witness cannot be asked to state, outright, whether a doctor’s behaviour
has fallen short of that expected by a professional doctor. However, it is easy
to see how a particular line of questioning by an advocate might elicit an
inference from an expert that is not too far removed from an opinion on the
ultimate issue.

In 2006 we reported on cases that dealt with
the emerging science of human memory research, particularly the reliability or
otherwise of childhood recollection (see Your Witness 45). In R -v-
S:R -v- W 4, the appellants sought to adduce fresh evidence from
an expert in human memory. Both had been convicted of sexual offences against
children. The two children in question had been aged between 6 and 8 and 3 and
11 years at the time of the offences, but were aged 20 and 27 years
at the time of trial.

The fresh evidence concerned childhood amnesia. It sought
to show that the detail contained in the witness statements was such that it
could not be consistent with normal childhood memories and was consequently
unreliable. In considering whether such evidence should be admitted, the court
was concerned that the nature of the evidence spoke to the ultimate issue in
the cases. If the expert witness evidence was accepted, it would tend to
suggest that the victims’ statements could not have been based in fact but,
instead, were likely to have been fabricated, whether consciously or otherwise.
The truthfulness of the victims’ statements was a question for the jury and not
for expert evidence. Accordingly, the appeal was dismissed and the fresh
evidence was not allowed.

Facing
facts

Facial mapping is another area where the courts
have considered the admissibility of expert evidence on the ultimate issue.

In R -v- Gray5, the Court of
Appeal held that, because there was no evidence of a national database of
facial characteristics, or any accepted statistical formula for determining the
probable occurrence of a particular characteristic or combination of
characteristics, an expert witness should not go further than to say that the
accused and the offender shared certain facial characteristics; he should not
seek to opine on whether the evidence provided ‘strong support’ of
identification of the accused. The cogency of the expert opinion in relation to
identification was a matter for the jury.

However, more recently in R -v- Mitchell 6,
it was accepted that a facial mapping expert can give an opinion on the
likelihood that the accused is the offender if the jury is shown (and provided
with) high-quality images and has the matches pointed out to them. This is
particularly so if the judge gives an adequate direction on the evidence.

Mitchell was
followed by the court in the case of R
-v- Atkins 7, where the judge allowed a facial mapping
expert to provide an assessment of the likelihood that the accused was the
offender, notwithstanding the absence of a national database of facial
characteristics. It was held that the limit imposed by Gray could
actually result in the jury giving too much weight to the evidence – a
result the judgment had been designed to avoid.

The only safeguard for the accused is that the
trial judge must explain to the jury in clear terms that a facial mapping
expert’s opinion is not based upon a database but is a subjective opinion
founded on experience.

Learned
opinion is against the rule

Academic lawyers have commented unfavourably on the
continued existence of the rule. It has been said to be wholly antithetical to
the underlying justification for having expert witnesses, namely that ‘the
drawing of inferences from the facts in question calls for an expertise which
the tribunal of fact does not possess’.

The sort of quasi-existence of the rule brings
its own problems. In R -v- Stockwell 8, the Court of Appeal
accepted that if there was a rule prohibiting experts from giving an opinion on
an ultimate issue, ‘... it has long been more honoured in the breach than the
observance’. Indeed, in the light of recent case law, there can no longer be
any doubt that an expert witness is able to give his opinion on an ‘ultimate
issue’ in criminal proceedings, so long as that opinion is within the area of
his expertise and the judge makes it clear that it is for the jury to decide
the issue. In other words, the jury can hear the expert’s view but choose to
ignore it.

The leading authorities on evidence, too, have
suggested that the rule is effectively dead. Archbold (2004, 10–66,
p.1287) states that:

‘... an expert
is now permitted to give his opinion on what has been called ‘the ultimate
issue’, but the judge should make it clear to the jury that they are not bound
by the expert’s opinion, and that the issue is for them to decide’.

This is echoed in Keane on Evidence at
pp. 507–508, which notes that:

‘... the
prohibition against ultimate issue testimony has become largely irrelevant.’

The rule has, however, been a fairly tenacious
one and is still capable of exerting some residual force. Mark Twain said, upon
learning that his obituary had been published in the New York Journal,
‘... the reports of my death have been greatly exaggerated’. One is left to
wonder whether the same might be said for the ultimate issue rule.